1. Field of the Invention
The present invention relates to a monitoring apparatus and method of a battery contact point that autonomously measures contact resistances of a contact terminal for directly connecting a battery for charging/discharging and a circuit in a charge/discharge apparatus for charging/discharging a single secondary battery or a plurality of secondary batteries in a row.
2. Description of the Related Art
A contact terminal directly contacting a battery in a battery charging/discharging circuit may experience degradation in contactability due to various reasons such as extraneous substances and an oxide film forming on a metal surface over a period of time, thereby causing heat to be generated during a process of charging/discharging, and possibly causing a fire. Typically, a battery contact point is disposed at a position that is difficult to observe through unaided eyes, and noticing a change in a contact resistance is therefore usually quite difficult.
Conventional charge/discharge apparatuses for a secondary battery may determine a presence of an abnormality in a contact resistance by measuring an intrinsic voltage of a battery and a phase difference occurring at a contact point during charging/discharging. In this instance, the conventional charge/discharge apparatuses may further require an expensive precision voltage measuring circuit in order to measure the contact resistance, thus leading to an increase in cost and time.
In a conventional method of precisely measuring a contact resistance of a battery in a region in which the contact resistance is provided in a unit of milliohm (mΩ), a battery is connected, a predetermined amount of current, typically within a range from a few amperes (A) to tens of A in which a mΩ resistance is measurable. Such measuring is often conducted during a relatively short period of time insufficient for heat to be generated, for example, typically for “0.01” to “1” second. An output voltage of a source device during the conducting may be compared to a voltage measured by a battery management system (BMS), and the contact resistance is calculated based on Ohm's law.
In this example, a voltage measuring instrument in an isolated type or a differential type structure is required to precisely measure the output voltage of the source device. Also, the conventional method may face difficulty in that a number of expensive precision measuring instruments corresponding to a number of batteries are required because a contact resistance of a battery contact point is in units of mΩ and a voltage of the battery contact point is merely in the range from a few mV to tens of mV. As a result, volume and weight of the voltage measuring instrument may increase and time and costs consumed for measuring may also increase correspondingly.
Korean Patent Publication No. 1997-0007366 discloses an apparatus and method of measuring a crimped terminal contact resistance. Technical configurations of the apparatus and method of measuring the crimped terminal contact resistance include measuring a contact resistance by flowing a large current between a crimped terminal and a conductor and measuring a voltage drop between the crimped terminal and an electric line, or measuring a calorie generated on a contact surface.
Korean Patent Publication No. 2000-0071372 discloses an apparatus and method of measuring an electric resistance of a circuit substrate. Technical configurations of the apparatus and method of measuring the electric resistance of the circuit substrate includes measuring an electric resistance applicable to a circuit substrate having an electrode in a small size or pitch using a current supplying electrode and a voltage measuring electrode.